Fix linux dawn roll

As in other places, we need to #undef Bool for X11

Bug: tint:741
Change-Id: I0185ed3c252f540212504b88859c600618fbfe23
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48961
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>

src/typepair.h

@@ -19,6 +19,12 @@
 #ifndef SRC_TYPEPAIR_H_
 #define SRC_TYPEPAIR_H_
 
+// X11 likes to #define Bool leading to confusing error messages.
+// If its defined, undefine it.
+#ifdef Bool
+#undef Bool
+#endif
+
 namespace tint {
 
 namespace ast {